Preparation - To prepare for the exploration, in 1803 Meriwether Lewis studied with leading scholars at the American Philosophical Society in Philadelphia, Pennsylvania on a wide range of science topics including astronomy, botany, zoology, and medicine. Lewis then assembled supplies and armaments and recruited boatmen from Harpers Ferry, West Virginia, Philadelphia, and Pittsburgh Pennsylvania. In Pittsburgh Lewis oversaw the construction of his specially designed 55-foot keelboat that would be used on the journey.

Recruitment - Journeying from Pittsburgh down the Ohio River, Lewis, and co-commander, Captain William Clark recruited men from American forts along the Ohio and Mississippi Rivers. The expedition members set up winter quarters in December 1803 on the Wood River in Illinois, opposite the mouth of the Missouri River.

Exploration - The Corps of Discovery traveled up the Missouri River, over the Rocky Mountains and down the Snake and Columbia Rivers. In November 1805, they reached their ultimate destination, the Pacific Ocean. In 1806 they returned all the way to St. Louis.